The detection of optical polarization state change effects is well known. Such effects include optical rotation, circular dichroism, linear dichroism, optical activity, and Kerr effect. For example, optical rotation can be measured with a polarimeter for measuring concentration, purities and specific rotation which is a fundamental property of matter of certain compounds such as large organic molecules, pharmaceuticals, flavors, fragrances and sugar.
The limit of measurement of optical rotation by the best known apparatus today that are practical to build in quantity, is of the order of 0.0001.degree. of measured rotation but the most practical apparatus has a sensitivity of only 0.001.degree.. There are many applications where a more sensitive measurement capability is necessary or desirable, as in high pressure liquid chromatography and other applications where the concentration of the sample is very low or the materials constants are very low and where the concentration cannot be increased because of the limited volume of the sample available or in the analyzing of waste water where there is no control of the concentration. Waste water analysis can be used in various pharmaceutical plants to assure no contamination of waste water with optically active materials. In the sugar industry, boiler water analysis can be employed to determine if there are any leaks of the reactants or purification vessels that allow sugar solution into the heat exchangers and the cooling water.
One solution to the problem of detecting very small optical rotations has been suggested by Yeung et al. in U.S. Pat. No. 4,498,774. However, the apparatus disclosed therein, with present manufacturing limitations, is not practical to produce in quantity. Thus, there is a need for an improved apparatus and method for detecting very small optical polarization state change effects such as optical rotations of less than 0.0001.degree., which apparatus can be produced in quantity.